1. Field of the Invention
The invention relates to devices for measuring a parameter capable of modifying an electrical charge borne by an electret. Such a parameter may be one of the following:
an ionizing radiation (gamma rays, x-rays, neutrons) capable of gradually discharging the electret, or of creating ions in the vicinity of this electret and thus of covering it gradually with an ion layer neutralising its charge, PA1 the concentration of a fluid, such as an organic vapor or liquid, adapted to gradually discharge the electret on being placed in contact with the latter, PA1 a temperature.
2. Description of the Prior Art
The invention relates more particularly, among these devices, to those including, in addition to the electret, two conductive electrodes framing this electret parallel to the latter, a separating part keeping at least one of these electrodes at a certain distance from the electret so as to reserve a chamber between them, means to enable the parameter to be measured to exert its influence in this chamber thereby modifying the charge of the electret, an electrical circuit for measuring the modifications in the electrical field produced in the chamber, a conductive flap or shutter and means for moving this shutter inside the chamber parallel to itself and to the electrodes from a watching or stand-by position to a measuring position and conversely.
It is a particular object of the invention to render measuring devices of the type concerned such that they respond to the various exigencies of practice better than hitherto, notably in that they are accurate, simple, effective, and portable, at least as regards the chamber of the electret, and inexpensive to manufacture and to use.